Most shoes are purchased because of their aesthetics or their comfort. Comfort shoes are designed to provide comfortable walking and standing for a user and often include reasonable internal padding, arch support and comfort soles. In normal use, prior art shoes provide a good stable base for a foot of a user and this, consequently, reduces the amount of muscle force required for a user to stand still or walk, whilst maintaining good balance.
However, it has surprisingly been found that, by providing a slight, but safely-measured, instability in the footwear, the amount of difficulty a user experiences balancing whilst walking or standing is increased and, therefore, more muscle activity is required to achieve equivalent good balance to when using prior art shoes. In particular, muscles such as tibialis anterius, tibialis posterior, rectus femoris muscles of the quadriceps and gluteus maximus have been found to work harder whilst wearing footwear having a slight instability. Further, as is well-known in human physiology, a muscle which is made to work harder improves in strength and has quicker recovery following exercise.